Re: Upgrade from 2.2.3 to 2.3 "ERROR: column "picture" contains null values"

First of all, to select the lines that you wanted, the right SQL query is:

SELECT id FROM mdl_user WHERE picture IS NULL;

I had the same problem when upgrading from 2.2 to 2.3, but I think this was due to the fact that my moodle database is really old (from 1.2, if I remember right).  I solved it with:

UPDATE mdl_user
SET picture = 0
WHERE picture IS NULL;